To easily mount a diffuser while restricting increase of size in a radial direction by protruding at least part of the diffuser into the scroll passage in a blower for introducing wind from a centrifugal impeller to a scroll passage via a diffuser.

An open type centrifugal impeller 30 mounted on a powered spreader carried on a back has a main plate 58 extending nearly parallel to an engine side portion 36 and an impeller portion 60 fixed to the main plate 58 and extending in the axial direction toward a suction port side portion 38. A portion 54 extending inside in the radial direction is disposed opposite to the peripheral portion of the main plate 58 with a small gap therebetween to form an inner circumferential portion of the engine side portion 36 of a scroll casing 40. The extending portion 52 of the suction port side portion 38 is extended straight in the radial direction and is plunged into a scroll passage 42 to constitute with the portion 54 extending inside in the radial direction a diffuser 56 surrounding the outside in the radial direction of the extending impeller 30.